Because life happened to Earth, its atmosphere, surface, and planetary crust have been profoundly altered again and again for some 4 billion years. Billions of years ago microbial life built an oxygen-rich atmosphere. There are signs that part of that process may have helped plunge Earth into a ‘snowball’ state – a period of profoundly cooler global climate for hundreds of millions of years. Ocean chemistry has been reworked by life. Cloud formation is influenced by biologically produced particles. Some scientists have even posited that microbe produced material could influence plate tectonics; the slip and slide of planetary crust.
In some respects, continues astrophysicist Caleb A. Scharf, Director of Astrobiology at Columbia University in Scientific American, humans are entirely trivial by comparison. One can argue that the Earth doesn’t care about us, nor will our behaviors provide much more than a blip on a much deeper history and future. In a hundred million years time there will likely still be life on Earth, it just won’t be the same life that is here now.
Except those blips are not quite so inconsequential. There have only been 5 mass extinctions of life in the past 500 million years – times at which over 80% of all species of complex life have disappeared. Today there is considerable evidence that a sixth such extinction event is underway, directly correlated to human activity. A very large part of that activity is the active geo-engineering of Earth’s climate due to a relentless release of greenhouse gases from fossil fuels.
And therein lies the critical point. Our established order, our human flourishing, has to this point taken place under a range of environmental conditions that are quickly vanishing. There’s a chance that we’ll be among the species that don’t make it through.
Image credit: With thanks to awramba.com
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